linux-kernel - Re: [PATCH v4 3/6] mm: drop per-VMA lock when returning VM_FAULT_RETRY or VM_FAULT

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Date:   Wed, 28 Jun 2023 09:41:31 -0400
From:   Peter Xu <peterx@...hat.com>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     akpm@...ux-foundation.org, willy@...radead.org, hannes@...xchg.org,
        mhocko@...e.com, josef@...icpanda.com, jack@...e.cz,
        ldufour@...ux.ibm.com, laurent.dufour@...ibm.com,
        michel@...pinasse.org, liam.howlett@...cle.com, jglisse@...gle.com,
        vbabka@...e.cz, minchan@...gle.com, dave@...olabs.net,
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        apopple@...dia.com, ying.huang@...el.com, david@...hat.com,
        yuzhao@...gle.com, dhowells@...hat.com, hughd@...gle.com,
        viro@...iv.linux.org.uk, brauner@...nel.org,
        pasha.tatashin@...een.com, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com
Subject: Re: [PATCH v4 3/6] mm: drop per-VMA lock when returning
 VM_FAULT_RETRY or VM_FAULT_COMPLETED

On Wed, Jun 28, 2023 at 12:17:57AM -0700, Suren Baghdasaryan wrote:
> handle_mm_fault returning VM_FAULT_RETRY or VM_FAULT_COMPLETED means
> mmap_lock has been released. However with per-VMA locks behavior is
> different and the caller should still release it. To make the
> rules consistent for the caller, drop the per-VMA lock when returning
> VM_FAULT_RETRY or VM_FAULT_COMPLETED. Currently the only path returning
> VM_FAULT_RETRY under per-VMA locks is do_swap_page and no path returns
> VM_FAULT_COMPLETED for now.
> 
> Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>

Acked-by: Peter Xu <peterx@...hat.com>

-- 
Peter Xu